Is the use of mobile phones everyday linked with increased risk of brain cancer?

One needs to separate the question of increased risk with causality. There have been dozens of studies ranging from null results to increased risk on the ipsilateral side of the head where the phone is used. Rates of brain cancer have not increased in the last 20 years, or any increase found can be attributed to greater detection. Microwave radiation cannot damage DNA, and studies showing increased risks are often limited by study biases. Imagine if you were unfortunate enough to have received a diagnosis of a tumor on the right side of the head and then were questioned about which side of the head you used your phone. Even a small percent of patients who might not recall their usage pattern accurately and report right-sided usage when they were in fact left-handed users would result in a spurious finding of an increased risk.

It's a fair question since nearly everyone worldwide now owns a mobile device. The weight of the evidence indicates that mobile phones do not cause cancer and other health issues other than traffic and pedestrian accidents.